Random Hacks comments
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en-us40Technology and Other Fun Stuff"Screencast: Use Rails and RDF.rb to parse Best Buy product reviews" by Gregg Kellogg<p>Great demo Eric! For another take on parsing Best Buy data, use http://rdf.greggkellogg.net/distiller (source available on GitHub as rdf-portal), also using the <span class="caps">RDF</span>.rb gems, to generate <span class="caps">HTML</span>+RDFa (or any other serialization) marked up with the same information as the search requests.</p>
<p>Also, we do have <span class="caps">SPARQL</span> support, but not in the released versions yet. Check out http://github.org/gkellogg/sparql-grammar, which uses the 0.4.x tag of <span class="caps">RDF</span>.rb to provide full <span class="caps">SPARQL 1</span>.0 support natively in Ruby.</p>
<p>Thanks for the great work and helping to show what a great environment for working with <span class="caps">RDF </span>Ruby really is.</p>
<p>Gregg</p>Wed, 08 Jun 2011 17:24:18 +0000urn:uuid:dda31477-ac22-41f3-a504-8e6d890a36de
http://www.randomhacks.net/articles/2011/06/05/screencast-rails-rdf-agraph-product-reviews#comment-856
"Derivatives of algebraic data structures: An excellent tutorial" by Frank Atanassow<p>@Eric I beg to differ. The article starts, “With the spreading popularity of languages like F# and Haskell, many people are encountering the concept of an algebraic data type for the first time. When that term is produced without explanation, it almost invariably becomes a source of confusion. In what sense are data types algebraic?”</p>
<p>So whereas they claim to explain in what sense an adt is algebraic, what they end up explaining is in what sense the kind * is algebraic.</p>Tue, 24 May 2011 20:30:41 +0000urn:uuid:315bc7f5-70f3-44f0-b350-3e2b12d3bc44
http://www.randomhacks.net/articles/2011/05/20/derivatives-of-algebraic-data-structures-an-excellent-tutorial#comment-843
"Derivatives of algebraic data structures: An excellent tutorial" by Eric<p>Aleksey, Steve: Thank you! I fixed the link.</p>
<p>Frank: Surely, among consenting category theorists, all isomorphic objects are identical. ;-) Thank you for the correction.</p>
<p>The article isn’t trying to explain algebraic data types by an analogy to differention. Rather, it’s trying to explain type differentiation, and it needs to define a loose algebra of types to get there.</p>Mon, 23 May 2011 13:04:02 +0000urn:uuid:bff740aa-3380-48aa-86aa-5fe377809c4c
http://www.randomhacks.net/articles/2011/05/20/derivatives-of-algebraic-data-structures-an-excellent-tutorial#comment-841
"Derivatives of algebraic data structures: An excellent tutorial" by Steve Massey<p>This is the same paper:</p>
<p>http://strictlypositive.org/Dissect.pdf</p>Sun, 22 May 2011 10:42:48 +0000urn:uuid:befc75bf-b0d4-444c-a5b2-b363276f6562
http://www.randomhacks.net/articles/2011/05/20/derivatives-of-algebraic-data-structures-an-excellent-tutorial#comment-840
"Derivatives of algebraic data structures: An excellent tutorial" by Aleksey Khudyakov<p>This link leads to 403 page. Is this paper available anywhere else?</p>
<p>http://www.cs.nott.ac.uk/~ctm/Dissect.pdf</p>Sat, 21 May 2011 14:08:02 +0000urn:uuid:f4105c04-9a23-4018-b76b-5fea2a4e80f2
http://www.randomhacks.net/articles/2011/05/20/derivatives-of-algebraic-data-structures-an-excellent-tutorial#comment-839
"Derivatives of algebraic data structures: An excellent tutorial" by Frank Atanassow<p>I only read the first half, and it looks like a nice tutorial, but it does not explain what it claims to explain, namely in what sense adt’s are algebraic.</p>
<p>Algebraic datatypes are not called algebraic because type constructors form an algebra, but rather because data constructors do. In fact, type constructors do not even form an algebra; they form a pseudo-algebra, which is a generalization of algebras. That is why properties like associativity of products only hold up to (unique, natural) isomorphism rather than up to type equality.</p>
<p>If you want to explain the algebraic nature of Haskell datatypes with an allusion to differentiation, you can do it by defining a datatype, say, of polynomials.</p>Fri, 20 May 2011 23:47:27 +0000urn:uuid:f84ba62e-37d3-43fb-85d9-92139044456b
http://www.randomhacks.net/articles/2011/05/20/derivatives-of-algebraic-data-structures-an-excellent-tutorial#comment-837
"What do these fixed points have in common?" by Eric<p>Thank you for the pointer! I’ll try to dig up those papers when I have time to play with this stuff a bit.</p>
<p>Some related links of interest:</p>
<p>1. The Wikipedia article on <a href="http://en.wikipedia.org/wiki/Fixed_point_theorem" rel="nofollow">fixed-point theorems</a>.</p>
<p>2. A MathOverflow question about the <a href="http://mathoverflow.net/questions/34511/banach-and-knaster-tarski-fixed-point-theorems-are-they-related" rel="nofollow">relation between two of the big fixed-point theorems</a>.</p>
<p>Nash equilibria can apparently be <a href="http://en.wikipedia.org/wiki/Nash_equilibrium#Alternate_proof_using_the_Brouwer_fixed_point_theorem" rel="nofollow">derived from Brouwer fixed points</a>, according to Wikipedia, but I haven’t read the proof yet.</p>Thu, 12 May 2011 17:24:18 +0000urn:uuid:ef259692-efde-4cbe-aa05-bbb9ed9cffee
http://www.randomhacks.net/articles/2011/05/12/what-do-fixed-points-have-in-common#comment-834
"What do these fixed points have in common?" by Derek Elkins<p>There’s a “small” (categorical) diagram that is rarely talked about that is relevant here. The popular examples are empty diagrams, finite diagrams of discrete points, parallel pairs of arrows, and wedges. The colimits of those are, respectively, initial objects, coproducts, coequalizers, and pushouts. There is another notable diagram however, the loop. Barry Jay has a couple of papers on the limits and colimits of a diagram of this form. I don’t know if this will capture all of these examples (in particular, the Nash equilibria would take a bit of twisting I’d think), but it certainly is a place to start.</p>Thu, 12 May 2011 17:02:07 +0000urn:uuid:b9c4d16d-54a0-4144-819b-18ab22b2744d
http://www.randomhacks.net/articles/2011/05/12/what-do-fixed-points-have-in-common#comment-833
"AWS outage timeline & downtimes by recovery strategy" by Eric<p>The links should be fixed. Thanks, linkchecker!</p>Mon, 25 Apr 2011 19:44:49 +0000urn:uuid:a551bba6-cd2b-40bf-8e8b-9f4703b22ccf
http://www.randomhacks.net/articles/2011/04/25/aws-outage-timeline-and-recovery-strategy-downtimes#comment-818
"AWS outage timeline & downtimes by recovery strategy" by linkchecker<p>Under “Lessons Learned”, #3, both links point to the reddit blog. Presumably one should point to Netflix instead.</p>Mon, 25 Apr 2011 16:56:45 +0000urn:uuid:b3348deb-8a96-4c8c-8210-c938d0c59070
http://www.randomhacks.net/articles/2011/04/25/aws-outage-timeline-and-recovery-strategy-downtimes#comment-817